JP2008157911A - Impedance measuring device - Google Patents

Abstract

An error generated in a signal conversion circuit included in an input system for a measurement signal can be surely canceled while simultaneously measuring a voltage signal and a current signal obtained from a sample to be measured.
When a signal conversion circuit converts each of a voltage signal and a current signal obtained from a sample to be measured into a predetermined signal form and gives the signal to the control means to obtain the impedance of the sample to be measured, two signals having the same configuration are used. Conversion circuits 100 and 200, and switches SW1 and SW2 for switching these signal conversion circuits to the voltage signal input channel 1 and the current signal input channel 2, and the signal conversion circuit 100 is connected to the voltage signal input channel 1 as a first step. , the calculated impedance Z ₁ connected to the signal conversion circuit 200 into a current signal input channel 2, as a second step, the signal conversion circuit 100 into a current signal input channel 2, the signal conversion circuit 200 a voltage signal input channels 1 connect calculates the impedance _{Z 2,} the measurement object from the impedance _Z 1, _{Z 2} Prefecture Determine the impedance Z of the sample.
[Selection] Figure 1

Description

  The present invention relates to an impedance measuring apparatus, and more particularly to a technique for eliminating an error component included in a signal conversion circuit of an impedance measuring apparatus.

  In the impedance measuring apparatus, an AC signal for measurement is applied from a signal source to a sample to be measured, and a voltage signal generated at both ends of the sample to be measured and a current signal flowing through the sample to be measured (this voltage signal and current signal are In some cases, the impedance of the sample to be measured is obtained by calculation.

  Since arithmetic processing means such as a CPU is used for this calculation, the measurement signal is converted into a digital signal by an A / D converter in the preceding stage, but even with an A / D converter having a high resolution, The sampling rate is said to be limited to several hundred ksamples / second.

  Therefore, as illustrated in FIG. 5, it is common to connect a frequency conversion circuit 12 to the previous stage of the A / D converter 11, convert the measurement signal to a predetermined frequency, and then input the signal to the A / D converter 11. (For example, refer to Patent Document 1).

The frequency conversion circuit 12 includes a multiplier (mixer) that multiplies the measurement signal (analog voltage signal and current signal obtained from the sample to be measured) by a modulation signal (frequency f _M ) from a local oscillator (not shown). ) 12a and a low-pass filter 12b.

This frequency conversion is a heterodyne system, and when the frequency of the measurement signal is f _A , a sum frequency signal (f _A + f _M ) and a difference frequency signal (f _A −f _M ) are output from the multiplier 12a. Therefore, the difference frequency signal is extracted as a signal under measurement by the low-pass filter 12b, the difference frequency signal is converted into a digital signal by the A / D converter 11, and then a control means comprising a CPU (arithmetic processing means) or the like. 20 is given.

In this case, the characteristics of the multiplier 12a and the low-pass filter 12b change with temperature, time, etc., as with other electrical / electronic components, and this may cause errors in measured values. Here, the error that occurs between the multiplier 12a and the low-pass filter 12b is (k _Err expjθ _Err ), but the A / D converter 11 that is said to have a relatively stable characteristic also has characteristics depending on temperature and time. May change.

Therefore, conventionally, as shown in FIG. 5, the frequency conversion circuit 12 is commonly used for the voltage signal (Vexpjθ _V ) and the current signal (Iexpjθ _I ), and the voltage signal and the current signal are converted to the frequency conversion circuit via the switch SW. 12 are given alternately.

According to this, when the impedance Z is calculated by the control means 20, the error (k _Err expjθ _Err ) included in the voltage signal and the current signal is canceled as shown in the following equation (1). become.

Japanese Patent Laying-Open No. 2004-294269 (FIG. 1)

  By the way, when white noise is included in the measurement signal, the stability of the measurement value is proportional to the square root of the measurement time. However, in the above conventional example, the voltage signal and the current signal are measured alternately. Is wasted.

  For example, if each measurement time of the voltage signal and the current signal is 1 ms, the total time for measuring both signals is 2 ms, but the actual measurement time is 1 ms for each signal, and the measured value is high and stable. There is a problem that sex cannot be obtained.

  Accordingly, an object of the present invention is to make it possible to reliably cancel errors generated in a signal conversion circuit included in an output system of a measurement signal while simultaneously measuring a voltage signal and a current signal obtained from a sample to be measured. There is.

In order to solve the above-mentioned problems, a first invention is a signal conversion circuit for converting each of a voltage signal and a current signal obtained from a sample to be measured into a predetermined signal form, as described in claim 1. And a control means for obtaining the impedance of the sample to be measured based on the converted voltage signal output from the signal conversion circuit and the converted current signal, It has two signal conversion circuits, selects either the voltage signal or the current signal and inputs it to the first signal conversion circuit, and selects either the voltage signal or the current signal. A second switch for inputting to the second signal conversion circuit, and the control means sets the first switch to the voltage signal side as the switch switching step. Are switched to the current signal side, the voltage signal is input to the first signal conversion circuit, the current signal is input to the second signal conversion circuit, and the first switch is connected to the current signal. And a second step of switching the second switch to the voltage signal side, inputting the current signal to the first signal conversion circuit, and inputting the voltage signal to the second signal conversion circuit. , the impedance Z ₁ is calculated from the above converted voltage signal and the converted current signal output from the respective signal conversion circuit in the first step, is output from the respective signal conversion circuit in the second step the square root √Z 1 _· Z ₂ of the product of the impedance Z ₂ is calculated from the voltage signal and the converted current signal after the conversion, obtains the impedance Z of the sample to be measured It is characterized in that.

  In the first invention, as described in claim 2, it is preferable that the first step and the second step are switched in the same cycle.

According to a second aspect of the present invention, as described in claim 3, each of a measurement signal source for applying an AC signal for measurement to the sample to be measured, and a voltage signal and a current signal obtained from the sample to be measured A signal conversion circuit for converting the signal into a predetermined signal form, and control means for obtaining the impedance of the sample to be measured based on the converted voltage signal and the converted current signal output from the signal conversion circuit, In the impedance measuring apparatus, wherein the conversion circuit includes a multiplier that multiplies each of the voltage signal and current signal obtained from the sample to be measured by the modulation signal from the local oscillator, and the output of the voltage signal is used as the signal conversion circuit. A first signal conversion circuit provided in the system and a second signal conversion circuit provided in the output system of the current signal, and different from the modulation signal of the local oscillator. A reference signal output unit that outputs a reference signal having a frequency, a first switch that selectively connects the first signal conversion circuit to either the voltage signal output system or the reference signal output unit, and the first switch A second switch for selectively connecting the two-signal conversion circuit to either the current signal output system or the reference signal output unit, and the control means performs the first and first switches as a switch switching step. The first step of switching both switches to the reference signal output unit side and inputting the reference signal to the first and second signal conversion circuits, and both the first and second switches to the output system side And the second signal converting circuit inputs the current signal to the second signal converting circuit, and the control means includes the first step. In the first, respectively calculated impedance Z ₃ from the converted reference signal outputted from the second signal converter circuit, converted voltage signal output from the first signal conversion circuit in the second step and the second After calculating the impedance Z ₄ from the converted current signal output from the signal conversion circuit, the impedance Z ₄ is divided by the impedance Z ₃ (Z ₄ / Z ₃ ) to obtain the impedance Z of the sample to be measured. It is characterized by seeking.

  In the second aspect, as described in claim 4, it is preferable that the reference signal output unit obtains the reference signal from the measurement signal source.

In addition, as described in claim 5, in the case where there are a plurality of the samples to be measured and each of them is sequentially transported to a measurement stage by a predetermined transport means, and impedance measurement is performed, preferably, the first step in the transfer of the sample to be measured is performed is the impedance Z ₃ is calculated, the impedance Z ₄ is the second step in the measurement after transported to the measurement stage execution is calculated.

According to the first invention, the first and second signal conversion circuits having the same configuration are provided. In the first step, of the voltage signal and the current signal, for example, the voltage signal is transferred to the first signal conversion circuit. In the second step, the current signal is input to the first signal conversion circuit and the voltage signal is input to the second signal conversion circuit, and the first signal is input to the second signal conversion circuit. From the square root √Z ₁ · Z ₂ of the product of the impedance Z ₁ calculated based on the measurement signal at the step and the impedance Z ₂ calculated based on the measurement signal at the second step, the impedance of the sample to be measured Since Z is obtained, the error of each signal conversion circuit is canceled in the calculation process while simultaneously measuring the voltage signal and the current signal obtained from the sample to be measured. Qualitative is obtained. Further, during the extremely short time from the start of measurement of the Z ₁ until the end of the measurement of Z _2, since it is sufficient stable, it can be inexpensively constitute a signal conversion circuit.

In addition, according to the second invention, in a first step, the first reference signal are both input to the second signal converter circuit, the impedance Z ₃ is calculated by the reference signal after the conversion, the second step follows in the voltage signal to a first signal conversion circuit is input, a current signal is input to the second signal converter circuit, the impedance Z ₄ are calculated by the voltage and current signals after their conversion, then the impedance Z ₄ By dividing by the impedance Z ₃ (Z ₄ / Z ₃ ) to obtain the impedance Z of the sample to be measured, the error of each signal conversion circuit is canceled in the calculation process as in the first aspect. Therefore, high stability of the measured value can be obtained. In addition, the reference signal and the signal conversion circuit can be configured at low cost because it is only necessary to be stable for a very short time from the start of the measurement of Z ₁ to the end of the measurement of Z ₂ .

  In the second invention, in the first step, voltage and current measurement signals are not required. For example, there are a plurality of samples to be measured, each of which is sequentially transported to the measurement stage by a predetermined transport means. When impedance measurement is performed, calibration data can be obtained by executing the first step during conveyance of the sample to be measured.

  First, a first embodiment of the present invention will be described with reference to FIG. 1, and then a second embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a portion of a signal conversion circuit in the impedance measuring apparatus according to the first embodiment. FIG. 1A shows a switch switching state at the first step, and FIG. 1B shows a state at the second step. The switch switching state is shown.

  As shown in FIG. 1, the impedance measuring apparatus according to the first embodiment is a signal path from each output channel of a voltage output channel (voltage output system) 1 and a current output channel (current output system) 2 to the control means 20. The first and second signal conversion circuits 100 and 200 are connected in parallel.

A voltage signal (Vexpjθ _V ) generated at both ends of the sample to be measured is supplied to the voltage output channel 1 from the measurement signal source 400 to the sample to be measured DUT (both see FIG. 2). In addition, a current signal (Iexpjθ _I ) flowing through the sample to be measured appears in the current output channel 2. As the control means 20, a CPU (arithmetic processing means), a microcomputer, or the like may be used.

  The first and second signal conversion circuits 100 and 200 have the same configuration. In this example, each of the signal conversion circuits 100 and 200 includes an A / D converter 110 and 210 and a frequency conversion connected to the preceding stage thereof. Circuits 120 and 220 are included.

The frequency converters 120 and 220 share the local oscillator 300, and a multiplier (mixer) that multiplies the modulation signal (frequency f _M ) from the local oscillator 300 and the measurement signal (voltage signal, current signal). 121 and 221 and low-pass filters 122 and 222 are included.

As in the conventional example described above, the frequency conversion is a heterodyne system, and the frequency of the measurement signal is f _A, and the sum frequency signal of (f _A + f _M ) from the multipliers 121 and 221 and (f _A −f _M ) is output, the low-pass filters 122 and 222 extract the difference frequency signal as a signal under measurement.

Note that an error that occurs in the frequency conversion circuit 120 of the first signal conversion circuit 100 due to temperature, time, or the like is k _e1 expjθ _e1, and an error that occurs in the frequency conversion circuit 220 of the second signal conversion circuit 200 is k _e2 expjθ _e2 . .

  The first signal conversion circuit 100 is selectively connected to either the voltage output channel 1 or the current output channel 2 via the first switch SW1, and the second signal conversion circuit 200 is also connected via the second switch SW2. Thus, it is selectively connected to either the voltage output channel 1 or the current output channel 2. Switching of each switch SW1, SW2 is controlled by the control means 20.

  In this impedance measuring device, the signal path from the voltage output channel 1 and the current output channel 2 to the control means 20 is switched by the switches SW1 and SW2, thereby canceling errors generated in the signal conversion circuits 100 and 200.

  Therefore, as a first step, as shown in FIG. 1A, the first switch SW1 is switched to the voltage output channel 1 side and the second switch SW2 is switched to the current output channel 2 side.

As a result, the voltage signal (Vexpjθ _V ) is subjected to predetermined frequency conversion by the frequency conversion circuit 120 of the first signal conversion circuit 100, converted to a digital signal by the A / D converter 110, and input to the control means 20. . The current signal (Iexpjθ _I ) is frequency-converted to a predetermined frequency by the frequency conversion circuit 220 of the second signal conversion circuit 200, converted to a digital signal by the A / D converter 210, and input to the control means 20.

Control means 20, by the following equation from these voltage and current signals (2) to calculate the impedance Z ₁ in the first step.

  Next, as a second step, as shown in FIG. 1B, the first switch SW1 is switched to the current output channel 2 side, and the second switch SW2 is switched to the voltage output channel 1 side.

Thus, the voltage signal (Vexpjθ _V ) is frequency-converted to a predetermined frequency by the frequency conversion circuit 220 of the second signal conversion circuit 200, converted to a digital signal by the A / D converter 210, and input to the control means 20. . The current signal (Iexpjθ _I ) is frequency-converted to a predetermined frequency by the frequency conversion circuit 120 of the first signal conversion circuit 100, converted to a digital signal by the A / D converter 110, and input to the control means 20.

Control means 20, by the following equation from these voltage and current signals (3) to calculate the impedance Z ₂ at the second step. Note that the measurement time in the second step is preferably the same as the measurement time in the first step.

After the measurement in the second step, the control means 20 obtains the square root √Z ₁ · Z of the product of the impedance Z ₁ in the first step and the impedance Z _{2 in} the second step as shown in the following equation (4). ₂ is calculated to obtain the impedance Z of the sample to be measured.

As can be seen from this equation (4), the error of the first signal conversion circuit 100 (k _e1 expjθ _e1 ) and the error of the second signal conversion circuit 200 (k _e2 expjθ _e2 ) are calculated by the calculation of the square root √Z ₁ · Z _2. However, in the case of the first embodiment, the voltage signal and the current signal are measured at the same time, and the measurement time is not wasted. Ratio) is about √2 times higher.

Note that the measurement time of the impedances Z ₁ and Z ₂ in the first step and the second step is a short time of about 1 ms, for example. If this time is about this time, the errors (k _e1 expjθ _e1 ), ( Since k _e2 expjθ _e2 ) is stable, it can be canceled by the above equation (4). In the above example, the first step is performed first and then the second step is executed. However, the second step may be performed first and then the first step may be performed. .

As another example, the absolute value | Z ₁ | of the impedance Z ₁ obtained in the first step is represented by the following equation (5.1), the phase θ ₁ thereof is represented by the following equation (5.2), The absolute value | Z ₂ | of the impedance Z ₂ obtained in two steps is represented by the following equation (6.1), and the phase θ ₂ thereof is represented by the following equation (6.2), and the following equations (7.1) and (7. 2), the impedance | Z | and the phase θ of the sample to be measured can also be obtained.

  In the first embodiment, the first and second signal conversion circuits 100 and 200 do not necessarily include the frequency conversion circuits 120 and 220. For example, only the A / D converters 110 and 210 are included. Form may be sufficient.

  Next, a second embodiment of the present invention will be described with reference to FIGS. In the description of the second embodiment, the same reference numerals are used for the same components as those in the first embodiment.

  As shown in FIG. 2, also in the impedance measuring apparatus according to the second embodiment, the voltage output channel (voltage output system) 1 and the current output channel (current output system) 2 reach the control means 20 from each output channel. First and second signal conversion circuits 100 and 200 are connected in parallel between the signal paths.

FIG. 2 shows a DUT to be measured and a measurement signal source 400. An AC signal for measurement is supplied from the measurement signal source 400 to the sample DUT to be measured, and a voltage signal (Vexpjθ _V ) generated at both ends of the sample to be measured appears in the voltage output channel 1 through the voltage amplifier 410. .

In the current output channel 2, a current signal (Iexpjθ _I ) flowing through the sample DUT detected by the current detection unit 421 appears via the current amplifier 420. As the control means 20, a CPU (arithmetic processing means), a microcomputer, or the like may be used.

  The first and second signal conversion circuits 100 and 200 have the same configuration. As in the first embodiment, each signal conversion circuit 100 and 200 is connected to the A / D converters 110 and 210 and their previous stages. Frequency conversion circuits 120 and 220 are included.

The frequency converters 120 and 220 share the local oscillator 300, and a multiplier (mixer) that multiplies the modulation signal (frequency f _M ) from the local oscillator 300 and the measurement signal (voltage signal, current signal). 121 and 221 and low-pass filters 122 and 222 are included.

As in the first embodiment, an error generated in the frequency conversion circuit 120 of the first signal conversion circuit 100 due to temperature, time, or the like is denoted as k _e1 expjθ _e1, and an error generated in the frequency conversion circuit 220 of the second signal conversion circuit 200 is Let k _e2 expjθ _e2 .

In the second embodiment, a reference signal output unit 440 that outputs a reference signal (Sexpjθ _s ) having a frequency different from that of the modulation signal of the local oscillator 300 is provided.

  In this case, the reference signal output unit 440 obtains the measurement AC signal generated from the measurement signal source 400 as the reference signal via the attenuator 430 in order to simplify the configuration. In this example, the reference signal is 1 MHz, and the modulation signal of the local oscillator 300 is set to 999 kHz.

  The first signal conversion circuit 100 is selectively connected to either the voltage output channel 1 or the reference signal output unit 440 via the first switch SW1, and the second signal conversion circuit 200 connects the second switch SW2. Through the current output channel 2 and the reference signal output unit 440. Switching of each switch SW1, SW2 is controlled by the control means 20.

  In the impedance measuring apparatus according to the second embodiment, the errors generated in the signal conversion circuits 100 and 200 are canceled by switching the switches SW1 and SW2 as follows.

  First, as a first step, as shown in FIG. 2A, both the first switch SW1 and the second switch SW2 are switched to the reference signal output unit 440 side.

As a result, the reference signal (Sexpjθ _s ) is subjected to predetermined frequency conversion by the frequency conversion circuit 120 of the first signal conversion circuit 100, and then converted to a digital signal by the A / D converter 110, and the converted reference signal (Sexpjθ) _s · k _e1 expjθ _e1 ).

The reference signal (Sexpjθ _s ) is frequency-converted to a predetermined frequency by the frequency conversion circuit 220 of the second signal conversion circuit 200, converted to a digital signal by the A / D converter 210, and the converted reference signal (Sexpjθ _s). K _e2 expjθ _e2 ) is input to the control means 20

Control means 20, each of these converted reference signal _{(Sexpjθ s · k e1 expjθ e1} ), by _{(Sexpjθ s · k e2 expjθ e2} ) from the following equation (8) to calculate the impedance _{Z 3} in the first step .

  Next, as a second step, as shown in FIG. 2B, the first switch SW1 is switched to the voltage output channel 1 side, and the second switch SW2 is switched to the current output channel 2 side.

As a result, the voltage signal (Vexpjθ _V ) is subjected to a predetermined frequency conversion by the frequency conversion circuit 120 of the first signal conversion circuit 100, and then converted to a digital signal by the A / D converter 210, and the converted voltage signal (Vexpjθ) _V · k _e1 expjθ _e1 ) is input to the control means 20.

Further, the current signal (Iexpjθ _I ) is subjected to predetermined frequency conversion by the frequency conversion circuit 220 of the second signal conversion circuit 200, then converted to a digital signal by the A / D converter 110, and the converted current signal (Iexpjθ _I). K _e2 expjθ _e2 ) is input to the control means 20

Control means 20, by the following equation from the voltage signal and the current signal after these conversion (9), calculates the impedance Z ₄ in the second step.

After the measurement in the second step, the control means 20, as shown in the following equation (10), the impedance _{Z 4} in the second step is divided by the impedance _{Z 3} in the first step _(Z 4 / _{Z 3)} calculation Then, the impedance Z of the sample DUT to be measured is obtained.

As seen from this equation _{(10), (Z 4 /} Z 3) by calculation of the error _{(k e1 expjθ} e1) of the first signal conversion circuit 100, the second signal converter 200 error _{(k e2 expjθ} e2 ) And are deleted.

  Thereafter, the first step and the second step are repeatedly executed for each sample DUT to be measured. In the second embodiment, as shown in FIG. 3, each sample DUT1, DUT2, and DUT are measured. It is particularly preferably applied to a measurement process in which DUTs 3,... Are sequentially carried to the impedance measuring unit M by a predetermined conveying means C and measurement is performed.

That is, as shown in the flow of the measurement process in FIG. 4, the first step is executed during conveyance to obtain the impedance Z ₃ (calibration data) based on the reference signal, and the impedance measurement unit M measures the voltage and current. by obtaining the impedance Z _4, it is possible to make a reasonable impedance measurement.

The reference signal in the second embodiment, since it is sufficient that the very short time stable up finishes measuring the impedance Z ₄ from the start at least the measurement of the impedance Z _3, a reference signal output section 440 low-cost Can be configured.

As another example, as in the first embodiment, the absolute value | Z ₃ | of the impedance Z ₃ obtained in the first step is expressed by the following equation (11.1), and the phase θ ₃ is expressed by the following equation (11 .2), the absolute value | Z ₄ | of the impedance Z ₄ obtained in the second step is represented by the following equation (12.1), and its phase θ ₄ is represented by the following equation (11.2). 13.1) and (13.2) can also determine the impedance | Z | and the phase θ of the sample to be measured.

The block diagram which shows the principal part of the impedance measuring apparatus which concerns on 1st Embodiment of this invention. The block diagram which shows the principal part of the impedance measuring apparatus which concerns on 2nd Embodiment of this invention. The schematic diagram which illustrated the measurement process in which the impedance measuring device concerning the 2nd embodiment is applied suitably. The flowchart which showed the measurement procedure implemented at the measurement process of FIG. The block diagram which shows the part of the signal conversion circuit in the conventional impedance measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Voltage output channel 2 Current output channel 20 Control means 100 1st signal conversion circuit 200 2nd signal conversion circuit 110,210 A / D converter 120,220 Frequency converter 121,221 Multiplier 122,222 Low pass filter 300 Local oscillator SW1, SW2 Switch 400 Measurement signal source 440 Reference signal output unit DUT Sample to be measured

Claims (5)

A signal conversion circuit that converts each of a voltage signal and a current signal obtained from the measured sample into a predetermined signal form, and the measured signal based on the converted voltage signal and the converted current signal output from the signal conversion circuit. In an impedance measuring device comprising a control means for obtaining the impedance of a sample,
A first switch that includes two first and second signal conversion circuits, selects one of the voltage signal and the current signal, and inputs the selected signal to the first signal conversion circuit; and the voltage signal; A second switch that selects any one of the current signals and inputs the current signal to the second signal conversion circuit;
The control means switches the first switch to the voltage signal side, the second switch to the current signal side, and inputs the voltage signal to the first signal conversion circuit as a switch switching step, A first step of inputting the current signal to the second signal conversion circuit;
The first switch is switched to the current signal side, the second switch is switched to the voltage signal side, the current signal is input to the first signal conversion circuit, and the voltage signal is input to the second signal conversion circuit. A second step of inputting,
The impedance Z ₁ is calculated from the converted voltage signal and the converted current signal output from the respective signal conversion circuit and in the first step, said output from each of the signal conversion circuit in the second step An impedance measuring apparatus, wherein the impedance Z of the sample to be measured is obtained by a square root √Z ₁ · Z ₂ of a product of the converted voltage signal and the impedance Z ₂ calculated from the converted current signal.   The impedance measuring apparatus according to claim 1, wherein the first step and the second step are switched at the same cycle. A measurement signal source that applies an AC signal for measurement to the sample to be measured, a signal conversion circuit that converts each of the voltage signal and current signal obtained from the sample to be measured into a predetermined signal form, and an output from the signal conversion circuit And a control means for obtaining the impedance of the sample to be measured based on the converted voltage signal and the converted current signal, and the signal conversion circuit is local to each of the voltage signal and the current signal obtained from the sample to be measured. In an impedance measuring device including a multiplier for multiplying a modulation signal from an oscillator,
The signal conversion circuit includes a first signal conversion circuit provided in the voltage signal output system and a second signal conversion circuit provided in the current signal output system, and a modulation signal of the local oscillator A reference signal output section for outputting a reference signal of a different frequency, a first switch for selectively connecting the first signal conversion circuit to either the voltage signal output system or the reference signal output section, A second switch for selectively connecting the second signal conversion circuit to either the current signal output system or the reference signal output unit;
The control means, as a switch switching step, switches both the first and second switches to the reference signal output unit side and inputs the reference signal to the first and second signal conversion circuits; The second step of switching both the first and second switches to the output system side, inputting the voltage signal to the first signal conversion circuit and inputting the current signal to the second signal conversion circuit. And
It said control means, the said first in first step, each calculated impedance Z ₃ from the converted reference signal outputted from the second signal converter circuit, is output from the first signal conversion circuit in the second step After calculating the impedance Z ₄ from the converted voltage signal and the converted current signal output from the second signal conversion circuit, the impedance Z ₄ is divided by the impedance Z ₃ (Z ₄ / Z ₃ ). An impedance measuring apparatus for obtaining an impedance Z of the sample to be measured.   The impedance measurement apparatus according to claim 3, wherein the reference signal output unit obtains the reference signal from the measurement signal source. In the case where there are a plurality of samples to be measured and each of them is sequentially transported to a measurement stage by a predetermined transport means and impedance measurement is performed, the first step is executed during transport of the sample to be measured, and the impedance is measured. Z ₃ is calculated, the impedance measuring apparatus according to claim 3 or 4, characterized in that the impedance Z ₄ is the second step is executed during measurement after transported to the measurement stage is calculated.

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